Soutenance de thèse de Shang GAO: Neutron scattering investigation of the spin correlations in frustrated spinels

Spinels of the chemical formula AB2X4 are important systems in the study of frustrated magnetism. The A and B sites of spinels constitute the diamond and pyrochlore lattices, respectively, whose geometries can give rise to many exotic phenomena. Here, I will present our investigations on the spin correlations in three types of spinels: the spin ice candidates CdEr2X4 (X = Se, S), the spiral spin-liquid candidate MnSc2S4, and the spin-Peierls system of MgCr2O4. Specifically, using inelastic neutron scattering and neutron diffuse scattering, we reveal the Ising character of the Er3+ spins in CdEr2X4 (X = Se, S) and confirm their ice correlations. For MnSc2S4, we directly observe the spiral surface using neutron diffuse scattering and discover an emergent vortex-like state using neutron diffraction. Finally, by combining neutron diffraction and spherical neutron polarimetry, the magnetic structure of MgCr2O4 are determined.